VS 2010 Web request login and go to other page and click a link

Hello i am new to web requests and so far i made my program login to a site.How i can go to another page of this site and click a link.
here is the code i used :

Imports System.Net
Imports System.Text
Imports System.IO

Public Class Form1

Dim logincookie As CookieContainer

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim postData As String = "referer=http%3A%2F%2Fforums.zybez.net%2Findex.php%3Fapp%3Dcore%26module%3Dglobal%26section%3Dlogin& username=" & TextBox1.Text & "&password=" & TextBox2.Text & "&rememberMe=1"
Dim tempCookies As New CookieContainer
Dim encoding As New UTF8Encoding
Dim byteData As Byte() = encoding.GetBytes(postData)

Dim postReq As HttpWebRequest = DirectCast(WebRequest.Create("http://forums.zybez.net/index.php?app=core&module=global&section=login&do=process"), HttpWebRequest)
postReq.Method = "POST"
postReq.KeepAlive = True
postReq.CookieContainer = tempCookies
postReq.ContentType = "application/x-www-form-urlencoded"
postReq.Referer = "http://forums.zybez.net/index.php?app=core&module=global&section=login&do=process"
postReq.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; ru; rv:1.9.2.3) Gecko/20100401 Firefox/4.0 (.NET CLR 3.5.30729)"
postReq.ContentLength = byteData.Length

Dim postreqstream As Stream = postReq.GetRequestStream()
postreqstream.Write(byteData, 0, byteData.Length)
postreqstream.Close()
Dim postresponse As HttpWebResponse

postresponse = DirectCast(postReq.GetResponse(), HttpWebResponse)
tempCookies.Add(postresponse.Cookies)
logincookie = tempCookies
Dim postreqreader As New StreamReader(postresponse.GetResponseStream())

Dim thepage As String = postreqreader.ReadToEnd

RichTextBox1.Text = thepage

End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
WebBrowser1.DocumentText = RichTextBox1.Text
End Sub

End Class